Common Misconceptions of human evolution



  • Our ancestors were chimpanzees: WRONG!
    • RIGHT: We share a common ancestor with chimps


  • Human evolution = series of steps from ancestor to Homo sapiens: WRONG!
    • RIGHT: Hominid phylogeny is more like bush than a ladder
    • Homo sapiens is a twig on the bush


  • Human characteristics like upright posture and large brain evolved together: WRONG!
    • RIGHT: Our ancestors include upright walkers with small brains

Primate phylogeny

The big picture: Humans are evolutionary newcomers

  • Our closest living relatives are the chimpanzees
    • common ancestor with chimps ~ 6-7mya
    • genomes are 98-99% similar to chimps
    • 1% difference means a lot!!
      • 19 regulatory genes differ
      • 600 genes differ in protein expression


  • Hominin derived characters:
    • bipedal
    • large brain…
    • reduce jawbone and jaw muscles
    • shorter digestive tract


  • These characters are not unique to Homo sapiens!

Hominins: part of primate family; includes genus Homo


  • ~20 species described (fossils) in the tribe
    • brain size, teeth shape, body size
    • inferred tool use/culture/language
    • species had different combos of each


  • Really old fossils
    • Sahelantrophus tchadensis (Toumai): 6.5mya
      • fossil connection to hominins missing
    • Ardipithecus ramidus (Ardi): 4.4 mya
      • lived in trees & on ground


  • We (Homo sapiens) are the sole surviving lineage

Hominin evolution was not a linear process

Hominin evolution:
brain volume

Hominin evolution: The jaw

Brainstorm: Why did we evolve to walk on 2 legs?

The earliest Hominins evolved in Africa


  • All but the 4 most recent species are found on the African continent


  • Oldest hominin fossil found in Chad
    • ~6-7 mya, found in 2001
    • diverged from common ancestor with chimps (~7mya)


  • Hominin diversity increased ~4-2 mya
    • Australopithecus genus
    • ‘Lucy’ fossil in Ethiopia
      • more diverse diet
    • definitely bipedal
    • gorilla-like shoulders: climbers
    • possible tool use

Lucy (Australopithecus afirensis) direct ancestor of Homo?

Homo genus in the fossil record


  • Early Homo genus is composed of first humans
    • all species are called humans
    • ~2mya to present day


  • 8-10 species described!
    • flat and narrow faces
    • small jaws and teeth
    • larger brain cases


  • Tool-making was their hallmark

Brain volume in Homo species increased disproportionately

Species of Hominins and Homo overlapped!

Homo species left Africa (H.ergaster then H.erectus)

Homo sapiens evolution


  • Descended from a 2nd wave of immigration out of Africa
    • ‘Out of Africa’ hypothesis
    • ~100,000 ya
    • fossil and DNA evidence
    • not the first species to leave


  • 1 population left Africa, split into 3 groups
    • 2,000 generations ago


  • Natural selection for the ability to reason and communicate
    • Increased tool use and language
    • resulted in larger brains

H.neandertalensis and H.sapiens co-occured


  • Neanderthals evolved in Eurasia
    • Split from a common ancestor ~ 500,000 ya
    • buried dead
    • used art


  • Co-existed until ~ 30,000 years ago
    • Middle East and Europe


  • Only one lineage survived
    • Interbreeding
    • Competition?
    • Extirpation of Neanderthals by modern humans?

H.neandertalensis and H.sapiens co-occured

Where is Human evolution heading?